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This study investigates the integration of word-initial fundamental frequency (F0) and voice-onset-time (VOT) in stop voicing categorization for adult listeners with normal hearing (NH) and unilateral cochlear implant (CI) recipients utilizing a bimodal hearing configuration [CI + contralateral hearing aid (HA)]. Categorization was assessed for ten adults with NH and ten adult bimodal listeners, using synthesized consonant stimuli interpolating between /ba/ and /pa/ exemplars with five-step VOT and F0 conditions. All participants demonstrated the expected categorization pattern by reporting /ba/ for shorter VOTs and /pa/ for longer VOTs, with NH listeners showing more use of VOT as a voicing cue than CI listeners in general. When VOT becomes ambiguous between voiced and voiceless stops, NH users make more use of F0 as a cue to voicing than CI listeners, and CI listeners showed greater utilization of initial F0 during voicing identification in their bimodal (CI + HA) condition than in the CI-alone condition. The results demonstrate the adjunctive benefit of acoustic hearing from the non-implanted ear for listening conditions involving spectrotemporally complex stimuli. This finding may lead to the development of a clinically feasible perceptual weighting task that could inform clinicians about bimodal efficacy and the risk-benefit profile associated with bilateral CI recommendation.

 

Continuous greenhouse gas monitoring at sub-zero temperatures is needed for monitoring greenhouse gas emission in cold environments such as the Arctic tundra. This work reports a single-frequency electrochemical impedance sensing (SF-EIS) method for real-time continuous monitoring of carbon dioxide (CO2) at a wide range of temperatures (−15 to 40 °C) by using robust ionic liquid (IL) sensing materials and noninvasive, low-power, and low-cost impedance readout mechanisms since they cause minimal changes in the sensing interface, avoiding the baseline change for long-term continuous sensing. In addition, a miniaturized planar electrochemical sensor was fabricated that incorporates a hydrophobic 1-butyl-1-methylpyrrolidinium bis(trifluromethylsulfonyl)imide ([Bmpy][NTf2]) IL electrolyte and Pt black electrode materials. The high viscosity of the ILs facilitates the formation of thin, ordered, and concentrated layers of ionic charges, and the inverse relationship of IL viscosity with temperature makes them especially suited for impedance sensing at low temperatures. The unique low-temperature properties of ILs together with EIS transduction mechanisms are shown to be sensitive and selective for continuously monitoring CO2 at a −15 to 40 °C temperature range via impedance changes at a specifically selected frequency at the open circuit potential (OCP). Molecular dynamics simulations revealed insights into the structure and dynamics of the IL at varying temperatures in the presence of methane and CO2 and provided potential explanations for the observed sensing results. The miniaturized and flexible planar electrochemical sensor with the [Bmpy][NTf2] electrolyte was tested repeatedly at subzero temperatures over a 58-day period, during which good stability and repeatability were obtained. The CO2 impedance sensor was further tested for sensing CO2 from soil samples and shows promising results for their use in real-time monitoring of greenhouse gas emissions in cold temperatures such as permafrost soils.